We’ve all the heard saying, “April Showers Bring May Flowers.” If that’s the case, what does all the May rain bring? This week it seems Northwest Indiana has been inundated with rain and cold temps and it has many concerned over their flower beds. Experts say heavy rains, particularly when they persist over an extended period, place stresses on plants in our landscapes.
The harm of excess
Since plants need water, what’s the issue with too much rain? Although soil may seem rather solid, there are lots of spaces between the particles. These spaces hold air and water, and the roots of plants need both. Roots absorb oxygen from the air spaces in the soil. When it rains or you water a plant growing in a container, all of the spaces in the soil fill with water, and the air is displaced. Gravity pulls on the water and it moves downward. As it does, air moves back into the soil spaces. If rain occurs frequently over an extended period, the air spaces in the soil are kept filled with water. This deprives the roots of the oxygen they need. If these conditions continue long enough, the roots stop functioning properly and may even begin to die. Although the soil is filled with water, the roots will not absorb it. This can cause plants to wilt, even though the soil is wet. At this point, the roots are also more vulnerable to attack by fungal organisms in the soil that cause root rot. Root rot infections are highly damaging to the roots and are often fatal.
The best defense
Our major defense against this happening is to make sure our landscape plants are growing in well-drained situations. Our primary tool to achieve this is planting in raised beds. Whether we are planting shrubs, bedding plants, perennials, vegetables or ground covers, the beds we prepare for them should be about 6 to 12 inches higher than the surrounding soil. Raised beds drain faster and dry out more quickly than ground-level beds. I hear gardeners complain during dry periods that raised beds may need to be watered more often — and this is often true. Still, we can irrigate and make sure plants have adequate water. But when it rains frequently and excessively over a long period, there is little we can do as gardeners to deal with the situation. Planting in raised beds, however, gives our landscape plants an added advantage. Creating a raised bed is typically accomplished when we turn the soil and add organic matter during bed preparation. The turning of the soil and the addition of several inches of organic matter elevates the bed about 6 inches. Or, beds are elevated when extra soil is brought in. Raised beds in landscapes typically do not have a structure, such as boards or bricks, enclosing the bed. In vegetable gardens, vegetables are planted in raised rows or raised beds. In raised rows, the soil in the garden is pulled up into long, rows elevated about 8 inches or more. Raised beds usually are enclosed with 2-by-12- inch boards.
So put on your rubber boots, grab an umbrella, and head outside! You will be able to clearly see how the water is flowing across your property, where it is exiting and what might be done to improve its movement off of your property. A licensed landscape architect can help design and install drainage when needed. Even with good drainage, you must choose plants that are adapted to the amount of rainfall we get.